1. Field of the Invention
The present invention relates to network terminal equipment wherein a plurality of communication control units can be installed in one terminal equipment, such as a workstation or the like, and more particularly to network terminal equipment, such as a workstation, that can accommodate a plurality of communication control units to permit connection by a plurality of protocols and/or to realize a dual configuration of the communication control unit.
2. Description of the Related Art
Each terminal equipment connected to a local area network (LAN), such as an Ethernet or an FDDI (fiber distributed data interface) network, is assigned a medium access control (MAC) address for uniquely identifying the terminal equipment in the network.
Conventionally, the MAC address has been assigned to each individual LAN control unit that is plugged into a slot in a workstation and that controls transmission and reception to and from LAN transmission channels. The MAC address is written in a ROM or like memory which is mounted on the LAN control unit. The reason that the MAC address is stored in a ROM or like memory is to prevent accidental alteration of the MAC address that could lead to a malfunction in the network.
If the LAN control unit has failed, it has to be replaced with a new unit. Since the same MAC address as that of the failed unit must be assigned to the new unit, the ROM holding the MAC address (hereinafter referred to as the MAC ROM) has to be removed from the failed unit and mounted on the new unit.
Previously, it has sometimes practiced to install the MAC ROM in the workstation itself, not on the LAN control unit. In such cases, if the LAN control unit has failed, it is simply replaced with a new unit.
If the known method described above is to be adopted for a workstation capable of accommodating a plurality of LAN control units in its slots to permit connection by a plurality of protocols and/or to realize a primary/spare dual configuration with two LAN control units, the workstation itself must be constructed to accommodate a plurality of MAC ROMs to correspond with the plurality of LAN control units. Furthermore, the plurality of MAC ROMs must have a one-to-one correspondence with the plurality of LAN control units to ensure the uniqueness of the MAC address. Moreover, when two LAN control units are used in a dual configuration, one as the primary and the other as the spare, the two control units must be constructed to be able to access a common MAC ROM, while disabling or prohibiting the operation of the spare LAN control unit by some means in order to ensure the uniqueness.